Put the flour in a food processor and add the butter. Blitz until the mixture resembles breadcrumbs. Add the rosemary and pulse briefly. Add the egg yolk and 2 tbsp chilled water. Blitz again, until the mixture comes together in a ball. If it remains crumbly, add 1 tbsp more water. Gently knead the pastry into a round disc and cover in clingfilm, then chill for 30 minutes.
Divide the pastry into four. Roll out one of the quarters until it’s around 2mm thick. You need to cut a circle 17cm in diameter and a circle 8cm in diameter from each section of pastry. It’s easiest to do this by cutting the large circle and then rerolling the off-cuts to cut out the smaller circle.
Place a little cheese in the centre of each large circle and gently bring up the pastry around the cheese, folding over the upper edges so it sits around the cheese. Brush the edges with a little of the beaten egg. Place 1 tbsp chutney in the middle of the cheese, then place the smaller circle on top. Pinch around the edges to seal the top to the sides, ensuring it is completely sealed. Check all around the pie to ensure the pastry hasn’t cracked anywhere and patch any hairline cracks with a little extra pastry. Using a knife, make a small incision in the top of the pie, then transfer to a lined baking tray. Repeat to make the remaining three pies. Return to the fridge and chill for 30 minutes.
Preheat the oven to 200°C/fan 180°C/gas mark 6. Remove the pies from the fridge and brush with the remainder of the beaten egg. Bake for 25 minutes until golden brown. Leave to rest for 5 minutes before serving.